Fire extinguishing system nozzle

ABSTRACT

The discharge outlet plug of a fire extinguishant nozzle is retained by an external lever system that is conditioned by the operation of a heat fusible means in response to the presence of a first temperature rise to permit release of the plug under fluid pressure in the nozzle. An overriding beam arrangement is provided to prevent release of the plug unless the nozzle fluid pressure exceeds a predetermined pressure floor, and in some forms a temperature responsive override arrangement is provided to disable the overriding beam arrangement in the presence of a materially higher temperature rise to permit the plug to be expelled by fluid pressures below the pressure floor.

United States Patent [191 Stamm et al.

111 3,823,779 [451 July 1 ,1974

FIRE EXTINGUISHING SYSTEM NOZZLE Inventors: Johann A. Stamm, Export; Siavash Eshghy, Pittsburgh, both of Pa,

Assignee: Factory Mutual Research Corporation, Norwood, Mass.

Filed: Jan. 30, 1973 Appl. No.: 327,960

US. Cl 169/39, 169/40, 169/42 Int. Cl. A62c 37/08 Field of Search 169/37-42 References Cited UNITED STATES PATENTS 9/1929 Doughty 169/38 12/1958 Dukes.

8/1972 Livingston 169/42 X Primary Examiner--M. Henson Wood, Jr.

Assistant Examiner-John J. Love Attorney, Agent, or FirmvLane, Aitken, Dunner & Ziems [5 7] ABSTRACT The discharge outlet plug of a fire extinguishant nozzle is retained by anexternal lever system that is conditioned by the operation of a heat fusible means in response to the presence of a first temperature rise to permitrelease of the plug under fluid pressure in the nozzle. An overriding beam arrangement is provided to prevent release of the plug unless the nozzle fluid pressure exceeds a predetermined pressure floor, and in some forms a temperature responsive override arrangement is provided to disable the overriding beam arrangement in the presence of a materially higher temperature rise to permit the plug to be expelled by fluid pressures below the pressure floor.

14 Claims, 8 Drawing Figures FMENTED JUL 1 81874 SHEET 1 0F 2 FIG. I

FIG. 3

PATENTEDJUHBIBH 3.823779 SHEEI 2 0F 2 FIG. 6

FIRE EXTINGUISHING SYSTEM NOZZLE This invention relates to spray nozzles for fire extinguishing systems of the type used in buildings for automatically discharging water or like liquid to an area where the ambient temperature may rise above a predetermined value, as in the case of a fire in that area, and is particularly directed to nozzles that are effective to discharge only when the internal or input fluid pressure is above a predetermined value which is sometimes identified as the pressure floor.

Fire extinguishing systems of this pressure floor type wherein even after a fusible control or like device has been actuated to release condition by increased temperatures due to fire are known and have been disclosed in the early U.S. Pats. to Doughty Nos. 1,736,255 and 1,736,256 as well as in the recently issued US. Pat. to Livingston No. 3,655,136.

The invention has as a major object the provision of a fire extinguishing system spray nozzle assembly wherein a blocking or closure member usually in the form of a plate-or a solid plug having one side exposed to force exerted by fluid pressure in the nozzle is main- 1 tained in the nozzle outlet by an externally mounted lever system that includes temperature responsive retaining means and an overriding beam holding arrangement for preventing the plug from being expelled from the outlet if the fluid pressure in the nozzle is below a predetermined pressure floor even though the level system is released by the temperature responsive means.

Another object of the invention is to provide, in the foregoing, overriding heat fusible means in the overriding beam that will act in the presence of a temperature higher than that which releases said temperature responsive retaining means to disable the holding action of the overriding beam and permit the blocking member to be expelled regardless of the degree of fluid pressure in the nozzle.

Further objects of the invention will appear in connection with the appended claims and the annexed drawings wherein:

FIG. 1 is a side elevation mainly in section showing the invention according to a preferred embodiment;

FIG. 2 is a side elevation similar to FIG. 1 but viewed in a section at right angles to FIG. 1 and showing the overriding beam;

FIG. 3 is a side elevation similar to FIG. 2 showing the overriding beam in a further embodiment;

FIG. 4 is a side elevation showing the overriding beam feature of the invention applied to an otherwise conventional type fire extinguisher nozzle;

FIG. 5 is a side elevation at right angles to FIG. 4 partly broken away and in section showing details of the pressure floor arrangement in that embodiment;

FIG. 6 is a side elevation partly broken away and in section similar to FIG. 5 showing another form of overriding beam incorporated in the otherwise conventional nozzle structure; V

FIG. 7 is a section substantially on line 7-7 of FIG. 6; and

FIG. 8 is a side elevation partly broken away and in section showing another form of the embodiment ofthe invention illustrated in FIG. 7.

PREFERRED EMBODIMENTS Referring to FIGS. land 2, the spray nozzle 11 com- 1 prises a tubular body 12 having an inlet designated at 13 threadedly connected to a supply pipe 14 that contains water under mains or pump pressure. A bladed swirl assembly S is fixed internally within the inlet to impart a swirling motion to water passing through the nozzle. The nozzle outlet designated at 15 is normally blocked by closure means in the form of a plug member 16 having an upwardly open external annular recess 17 around its periphery containing a compressed resilient O-ring 18 that seals against outlet passage of water under normal pressures. Plug member 16 has a slidable sealing fit in the outlet.

Plug 16 is retained in the nozzle outlet by an external lever system 19 that comprises a first lever 21 intermediately directly engaging the bottom of plug 16 and having one end hooked at 22 to rockably mount it upon an external annular nozzle body flange 23. The other end of lever 21 is pivoted on a fulcrum 24 on a second parallel lever 25 having a hooked end 26 rockably mounted ,on flange 23. Fulcrum 24 may be the rounded end of an adjustable screw 27 as shown. The other end of lever 25 has alug- 28 connected to a lug 29 on lever 21 by a heat fusible link 31. Link 31 preferably comprises metal elements 32 and 33 coupled by a heat fusible solder layer 34.

The lever system 19 also comprises an override beam unit 35 which as shown in FIG. 2 comprises laterally exwhich is laterally snugly disposed flat sided lever 21. A thin metal strap 42 extends across the bottom of recess' 41 to fixedly interconnect beam sections 36 and 37, and the opposite ends of strap 42 are-secured to the beam sections by heat fusible solder layers as indicated at 43. The fusion temperature of solder layers 43 is a predetermined amount higher than that of the layer 34 of link 31.

In operation, should a tire occur, link 31 will first fuse at a predetermined temperature thereby releasing and conditioning the lever system to permit the plug 16 to be expelled by fluid pressure. If the internal fluid pressure in the nozzle exceeds the predetermined pressure floor, the downwardly directed force acting through the plug and lever 21 will rupture strap 42 to break beam 35 into its separate components and permit the lever system to fall away from the outlet.

Should the pressure in the nozzle bebelow the pressure floor, beam 35 will hold the lever system in place and prevent the plug from being expelled. However, should the tire attain the higher temperature that fuses solder layers 43, the strap 42 will' separate from the beam and allow the lever system to drop away and the plug to be expelled regardless of the fluid pressure in the nozzle.

In order to ensure that the strap 42 will break at a desired pressure, the beam sections 36 and 37 are formed with relatively thin cross section substantially fixed pivot bending corners 44 and 45 respectively, and lever 21 is fitted into recess so that there is little or no lateral movement of beam sections 36 and 37 relative to lever 21 during transmission of force from plug 16 to strap 42. Thus the load pressure transmitted to strap 42 is positively maintained during finite movement of plug 16 through a predetermined distance so that rupture of strap 42 at a selected pressure floor is reliably and accurately possible. By eliminating lateral movement between beam sections 36 and 37 relative to lever 21, the effects of friction in the lever system are eliminated. As the fluid pressure force F acts downwardly on plug 16 it urges lever 21 solidly against beam section extensions 46 and 47 at the bottom of recess 41, so that the flexible beam sections are oppositely rocked about their bending corners. This places strap 42 in tension, and the cross section of strap 42 is so designed that it will break when subjected to tension force corresponding to the pressure floor.

FIG. 3 shows an embodiment similar to FIGS. 1 and 2 but wherein the override beam 48 comprises opposed component sections 49 and 51 having their inner ends spaced at 52 to define an upwardly open recess or space receiving lever 21, and across the lower end of space 52 extends the thin metal strap 53 secured at opposite ends by solder layers 54 to the beam sections. The outer ends of the beam sections in this embodiment are connected to the nozzle body flange 23 by wire or strap links 55 and 56 that are designed to act as hinges to insure that a tension force is applied to strap 53.

Also as shown'in FIG. 3, the inner ends of the beam sections may be formed with upstanding projections 57 and 58 directly positively engaging the beam sections so that the downward force exerted by plug 16 acts directly and positively on the pressure floor release device for optimum accuracy of operation. The operation is further the same as in FIGS. 1 and '.2 when the temperature exceeds the fusion point of solder layers 54, as this will separate strap 53 from the override beam and release the entire lever system regardless of the fluid pressure in the nozzle.

Referring now to FIGS. 4 and 5, the invention is shown as incorporated in a currently conventional type of fire extinguisher nozzle assembly comprising a generally ring shaped rigid body 60 having an externally threaded hollow boss 61 for mounting it on a water supply pipe and providing an inlet bore 62. As shown the upper outlet end of bore 62 is surrounded by an annular rim 63 upon which is seated closure plug means in theform of a sheet metal plate or disc .64 that has a shallow stepped central section 65 telescoped snugly within bore62. Below the central section 65 of plate 64, a retainer plate 66 slidably frictionally mounted in bore 62 holds compressed a resilient O-ring seal 67 in axial contact with plate 64 and in circumferential contact with bore 62, thus providing a fluid tight seal normally preventing undesired passage of water beyond plate 64 as will appear. The spring pressure of retainer plate 66 urges ring 67 in a direction to compress ring 67 to augment the seal while plate 64 is held seated on rim 63.

At the upper end 68 of body 60 is mounted a deflector 69. Temperature responsive retainer means for plate 64 is indicated at 70. It comprises an externally mounted lever system wherein separate levers 71 and 72 are intermediately pivoted together at 73 and held in assembly to urge their respective vertically aligned rounded end terminals 74 and 75 against the-rigid upper body end 68 and the central section of plate 64. A heat fusible link 76 connected between outer terminals 77 and 78 respectively of the levers holds the lever assembly in the normal arrangement shown in FIGS. 4 and 5.

In this embodiment the overriding beam arrangement comprises at least two relatively slender resilient metal beams 79 and 81 that are held in place by adjustable screws 82 and 83 respectively mounted in threaded bores 84 and 85 respectively. The beams 79 and 81 extend parallel to each other at opposite sides of the lever system and their lower ends abut plate 64 at about 180 spaced regions to solidly urge plate 64 onto seat 63. Beams 79 and 81, which may be small diameter rods of resilient metal, tend to hold plate 64 against displacement from seat rim 63 even when the link 76 has fused and levers 71 and 72 no longer exert a seating force on plate 64. Beams 79 and 81 are of such characteristics however that they will remain substantially rigid and hold closure plate 64 on its seat as long as the force exerted by the water inlet pressure in bore 62 upon plate 64 is lower than a predetermined pressure floor, but they will quickly buckle and release plate 64 to open the inlet bore if or when the inlet pressure exceeds the pressure floor value. Once beams 79 and 81 have buckled sufficiently to permit movement of the shallow center section of plate 64 out of bore 62, plate 64 along with retainer 66 and seal ring 67 and beams 79 and 81 will be blown clear of the inlet bore by water pressure and there is continuous flow of extinguishant through the nozzle assembly.

At their upper ends beams 79 and 81 are formed with tool receiving sockets such as screw drive slots 86 and 87 respectively, whereby the beams may be adjusted to equal and desired holding contact with plate 64. This adjustment predetermines the compressive force acting in each beam and thereby accurately sets the pressure floor.

In operation, normally link 76 biases levers 71 and 72 oppositely about their mutual pivot to spread their inner ends 74,75 into tight abutment with the nozzle body and plate 64 whereby plate 64 is maintained as a closure over the outlet end of bore 62. Should a fire occur in the vicinity, link 76will fuse at a predetermined temperature and release levers 71,72 whereby the nozzle assembly is conditioned to permit plate 64 to be forced out of and off the end of bore 62 by inlet fluid pressure. Displacement of plate 64 is however prevented by beams 79,81 unless the inlet water pressure is at or above the pressure floor value. When the inlet pressure exceeds the pressure floor value, beams 79,81 will buckle to permit displacement of closure plate 64 and unrestricted opening of the nozzle assembly for continuous passage of water therethrough.

FIGS. 6 and 7 illustrate incorporation of an overriding beam arrangement similar to that of FIGS. l-3 into otherwise conventional type fire extinguisher nozzles. In FIG. 6 the closure member for bore 62 is in the form of a solid plug 91 having an outer annular portion 92 seated on rim 63, a depending shallow central boss 93 telescoped slidably within the outlet end of bore 62 and an upstanding central post 94 in abutment with the inner terminal of lever 72 of the external lever assembly 71,72 which is the same as in FIGS. 4 and 5. Levers 71 and 72 are maintained in tight abutment with body 60 and plug 91 respectively by'a heat fusible link (not shown) as at 76 in FIG. 4.

The overriding beam assembly 95 comprises aligned two separate component beam sections 96 and 97 having their inner ends supported from below at 98 and 99 respectively on plug 91 so that they define between them an effective upwardly open flat sided recess 101 within which flat sided post 94 is laterally snugly received. The top surfaces of the outer ends of beam sections 96 and 97 abut inwardly projecting rigid integral lugs 102 and 103 respectively on body 60. A thin metal strap 104 which is like strap 42 'of FIG. 2 bridges the upper sides of the beam sections and opposite ends of strap 104 are secured to beam sections 96 and 97 respectively by heat fusible solder layers 105 and 106. Strap 104 is formed with a central opening 107 through which the lower end of lever 72 freely extends to abut the plug 91 as shown in FIG. 6.

A fluid pressure augmented seal is provided for bore 62, a retainer plate 108 and resilient seal ring assembly 109 being slidably frictionally disposed in bore 62 at the lower surface of plug 91.

In operation the parts are normally positioned as shown in FIG. 6 with levers 71 and 72 held in assembly by heat fusible link 76 with their inner ends spread to tightly abut body 60 and plug 91 and'thereby hold plug 91 seated on rim 63 to close bore 62. Beam sections 96,97 extend with substantially no'play between the' plug and the body, the fit of post 94 in recess 101 being essentially the same as that of lever 21 in recess 41 of FIG. 2. The resilient sea] at 109 at the lower end of the plug is augmented by inlet fluid pressure while the plug is held seated on rim 63.

Should a fire occur, levers 71 and 72 will be released by fusion of link 76 at a predetermined temperature, thereby conditioning the plug 91 to be displaced by water pressure in bore 62. However, should that pressure be below the predetermined pressure floor value, plug 91 will be maintained on its seat by the overriding beam to keep bore 62 closed. If the inlet pressure is at or above the pressure floor value the force exerted on the overriding beam through plug 91 will tension and rupture strap 104 thereby freeing the beam sections from restraint and permitting plug 91 to be displaced out of bore 62 by the water pressure.

The solder layers 105 and 106 correspond in function to layers 43 in FIG. 2 in that they are strong enough mechanically to secure the strap to the beam sections while the strap is under some tension, but they have an overriding fusion point a predetermined amount greater than that of link 76. Thus should the fire temperature increase to this higher amount the strap will release beam sections 96 and 97 to permit displacement of the plug 91 from its seat regardless of the degree of fluid pressure in bore 62.

The nozzle assembly shown in FIG. 8 is the same as in FIG. 6, except that a different seal arrangement is provided for closure plug 91. In this embodiment the retainer plate 108 of FIG. 6 is eliminated, and the resilient O-ring seal 109 is disposed in an annular downwardly open shouldered recess 111 around the lower end of the boss 93 that is slidably telescoped within bore 62.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being in What is claimed and desired to be secured by letters Patent is:

l. Fluid dispensing nozzle means comprising a body having a passage therethrough between an inlet adapted to be connected to a source of fluid under pressure and a discharge outlet, plug means normally blocking said outlet and having one side exposed to force exerted by said inlet fluid pressure, means for retaining said plug means in said outlet comprising a lever system mounted externally of said body and engaging said plug means, and beam means operable in cooperation with said lever system to prevent said plug means from being expelled from said outlet by said fluid pressure when said fluid pressure is below a predetermined value, said beam means incorporating a tension element interconnecting beam sections normally exerting a seating force on said plug means sufficient to close said passage and adapted to break when subjected to a force corresponding to said predetermined amount of fluid pressure to permit displacement of said plug means from said outlet.

2. The fluid dispensing nozzle means defined in claim 1, wherein said beam means comprises spaced beam sections rockably mounted on the body and interconnected by a metal tension strap comprising said tension element.

3. The fluid dispensing nozzle means defined in claim 1, wherein a heat fusible connection is provided betweem said beam sections and the tension element.

4. Fluid dispensing nozzle means comprising a body having a passage therethrough between an inlet adapted to be connected to a source of fluid under pressure and a discharge outlet, plug means normally blocking said outlet and having one side exposed to force exerted by said inlet fluid pressure, means for retaining said plug means in said outlet comprising a lever system mounted externally of said body and engaging said plug means, and flexible abutment means operable in cooperation with said lever system to prevent said plug means from being expelled from said outlet by said fluid pressure when said fluid pressure is below a predetermined value, said abutment means directly engaging said plug means and being-stiff enough for positively holding said plug means in a passage blocking position when said fluid pressure is below said predetermined amount, and being capable of flexing to permit passage opening displacement of said plug means when the plug means is; subjected to a force corresponding to fluid pressure at or above said predetermined amount.

5. The fluid dispensing nozzle means defined in claim 4, wherein said plug means is a closure plate extending over said passage outlet, and said releasable means comprises at least 'one flexible beam having opposite ends respectively abutting said body and the side of said plate opposite to that exposed to said fluid pressure exerted force, whereby said flexible beam is subjected to buckling by force transmitted through said plug means.

6. Fluid dispensing nozzle means comprising a body having a passage therethrough between an inlet adapted to be connected to a source of fluid under pressure and a discharge outlet, plug means normally blocking said outlet and having one side exposed to force exerted by said inlet fluid pressure, means for retaining said plug means in said outlet comprising a lever system mounted externally of said body and engaging said plug means, and releasable means operable in cooperation with said lever system to prevent said plug means from being expelled from said outlet by said fluid pressure when said fluid pressure is below a predetermined value, said releasable means comprising mechanism normally exerting a seating force on said plug means sufficient to close said passage but being yieldable to permit displacement of said plug means from said outlet when the plug means is subjected to a force corresponding to pressure at or above said predetermined amount in said nozzle, said mechanism being adjustable for presetting said releasable means to yield at a desired predetermined value.

7. Fluid dispensing nozzle means comprising a body having a passage therethrough between an inlet adapted to be connected to a source of fluid under pressure and a discharge outlet, plug means normally blocking said outlet and having one side exposed to force exerted by said inlet fluid pressure, plug retainer means comprising a lever system mounted externally of said body and engaging the other side of said plug means, releasable means for normally retaining said lever system in position to maintain said plug means in said passage blocking condition, said releasable means I being operable in response to the presence of predetermined temperature to condition said lever system to permit said plug means to be expelled from said outlet by said fluid pressure, and means separate from said lever system and directly engaging said plug means for normally maintaining a seating force on said plug means sufficient to maintain said passage closed but being yieldable to permit displacement of said plug means from said outlet when said plug means is subjected to force corresponding to pressure at or above a predetermined amount in said nozzle.

8. The fluid dispensing nozzle means defined in claim 7, wherein said means directly engaging said plug means comprises an overriding beam incorporating a tension element interconnecting separate beam sections and adapted to break only when subjected to a force corresponding to said predetermined amount of inlet fluid pressure.

9. The fluid dispensing nozzle means defined in claim- 7, wherein said means directly engaging said plug means comprises at least one beam member having opposite ends respectively engaging said body and said plug means and adapted to buckle in response to a force corresponding to said predetermined amount of inlet fluid pressure.

10. The fluid dispensing nozzle means defined in claim 8, wherein said beam sections are separately rockably mounted on the body and interconnected by a metal tension strap comprising said tension element.

11. The fluid dispensing nozzle means defined in claim 10, wherein heat fusible connections are provided between said beam sections and opposite ends of the tension element, said heat fusible connections being adapted to release interconnection between the tension element and said beam sections in the presence of a temperature that is a predetermined amount higher than said predetermined temperature.

12. Fluid dispensing nozzle means comprising a body having a passage therethrough between an inlet adapted to be connected to a source of fluid under pressure and a discharge outlet, plug means normally blocking saidoutlet and having one side exposed to force exerted by said inlet fluid pressure, plug retainer means comprising a lever system mounted externally of said body and engaging said plug means, releasably means for normally retaining said lever system in position to maintain said plug means in said passage blocking condition, said releasable means being operable in response to the presence of a first predetermined tem perature to condition said lever system to permit said plug means to be expelled from said outlet by said fluid pressure, means for holding the plug means in said blocking condition unless said fluid pressure is above a predetermined amount comprising an overriding beam incorporating a tension element interconnecting beam sections and adapted to break only when subjected to a force corresponding to pressure at or above said predetermined amount in said nozzle and means responsive to a temperature higher than said first predetermined temperature to release said last mentioned holding means and allow said plug means to be expelled irrespective of the value of said fluid pressure.

13. The fluid dispensing nozzle means defined in claim 12, wherein said beam comprises spaced beam sections rockably mounted on the body and interconnected by a metal tension strap comprising said tension element.

14. The fluid dispensing nozzle means defined in claim 12, wherein a heat fusible connection is provided between said beam sections and the tension element to provide said last mentioned release means. 

1. Fluid dispensing nozzle means comprising a body having a passage therethrough between an inlet adapted to be connected to a source of fluid under pressure and a discharge outlet, plug means normally blocking said outlet and having one side exposed to force exerted by said inlet fluid pressure, means for retaining said plug means in said outlet comprising a lever system mounted externally of said body and engaging said plug means, and beam means operable in cooperation with said lever system to prevent said plug means from being expelled from said outlet by said fluid pressure when said fluid pressure is below a predetermined value, said beam means incorporating a tension element interconnecting beam sections normally exerting a seating force on said plug means sufficient to close said passage and adapted to break when subjected to a force corresponding to said predetermined amount of fluid pressure to permit displacement of said plug means from said outlet.
 2. The fluid dispensing nozzle means defined in claim 1, wherein said beam means comprises spaced beam sections rockably mounted on the body and interconnected by a metal tension strap comprising said tension element.
 3. The fluid dispensing nozzle means defined in claim 1, wherein a heat fusible connection is provided betweem said beam sections and the tension element.
 4. Fluid dispensing nozzle means comprising a body having a passage therethrough between an inlet adapted to be connected to a source of fluid under pressure and a discharge outlet, plug means normally blocking said outlet and having one side exposed to force exerted by said inlet fluid pressure, means for retaining said plug means in said outlet comprising a lever system mounted externally of said body and engaging said plug means, and flexible abutment means operable in cooperation with said lever system to prevent said plug means from being expelled from said outlet by said fluid pressure when said fluid pressure is below a predetermined value, said abutment means directly engaging said plug means and being stiff enough for positively holding said plug means in a passage blocking position when said fluid pressure is below said predetermined amount, and being capable of flexing to permit passage opening displacement of said plug means when the plug means is subjected to a force corresponding to fluid pressure at or above said predetermined amount.
 5. The fluid dispensing nozzle means defined in claim 4, wherein said plug means is a closure plate extending over said passage outlet, and said releasable means comprises at least one flexible beam having opposite ends respectively abutting said body and the side of said plate opposite to that exposed to said fluid pressure exerted force, whereby said flexible beam is subjected to buckling by force transmitted through said plug means.
 6. Fluid dispensing nozzle means comprising a body having a passage therethrough between an inlet adapted to be connected to a source of fluid under pressure and a discharge outlet, plug means normally blocking said outlet and having one side exposed to force exerted by said inlet fluid pressure, means for retaining said plug means in said outlet comprising a lever system mounted externally of said body and engaging said plug means, and releasable means operable in cooperation with said lever system to prevent said plug means from being expelled from said outlet by said fluid pressure when said fluid pressure is below a predetermined value, said releasable means comprising mechanism normally exerting a seating force on said plug means sufficient to close said passage but being yieldable to permit displacement of said plug means from said outlet when the plug means is subjected to a force corresponding to pressure at or above said predetermined amount in said nozzle, said mechanism being adjustable for presetting said releasable means to yield at a desired predetermined value.
 7. Fluid dispensing nozzle means comprising a body having a passage therethrough between an inlet adapted to be connected to a source of fluid under pressure and a discharge outlet, plug means normally blocking said outlet and having one side exposed to force exerted by said inlet fluid pressure, plug retainer means comprising a lever system mounted externally of said body and engaging the other side of said plug means, releasable means for normally retaining said lever system in position to maintain said plug means in said passage blocking condition, said releasable means being operable in response to the presence of predetermined temperature to condition said lever system to permit said plug means to be expelled from said outlet by said fluid pressure, and means separate from said lever system and directly engaging said plug means for normally maintaining a seating force on said plug means sufficient to maintain said passage closed but being yieldable to permit displacement of said plug means from said outlet when said plug means is subjected to force corresponding to pressure at or above a predetermined amount in said nozzle.
 8. The fluid dispensing nozzle means defined in claim 7, wherein said means directly engaging said plug means comprises an overriding beam incorporating a tension element interconnecting separate beam sections and adapted to break only when subjected to a force corresponding to said predetermined amount of inlet fluid pressure.
 9. The fluid dispensing nozzle means defined in claim 7, wherein said means directly engaging said plug means comprises at least one beam member having opposite ends respectively engaging said body and said plug means and adapted to buckle in response to a force corresponding tO said predetermined amount of inlet fluid pressure.
 10. The fluid dispensing nozzle means defined in claim 8, wherein said beam sections are separately rockably mounted on the body and interconnected by a metal tension strap comprising said tension element.
 11. The fluid dispensing nozzle means defined in claim 10, wherein heat fusible connections are provided between said beam sections and opposite ends of the tension element, said heat fusible connections being adapted to release interconnection between the tension element and said beam sections in the presence of a temperature that is a predetermined amount higher than said predetermined temperature.
 12. Fluid dispensing nozzle means comprising a body having a passage therethrough between an inlet adapted to be connected to a source of fluid under pressure and a discharge outlet, plug means normally blocking said outlet and having one side exposed to force exerted by said inlet fluid pressure, plug retainer means comprising a lever system mounted externally of said body and engaging said plug means, releasably means for normally retaining said lever system in position to maintain said plug means in said passage blocking condition, said releasable means being operable in response to the presence of a first predetermined temperature to condition said lever system to permit said plug means to be expelled from said outlet by said fluid pressure, means for holding the plug means in said blocking condition unless said fluid pressure is above a predetermined amount comprising an overriding beam incorporating a tension element interconnecting beam sections and adapted to break only when subjected to a force corresponding to pressure at or above said predetermined amount in said nozzle and means responsive to a temperature higher than said first predetermined temperature to release said last mentioned holding means and allow said plug means to be expelled irrespective of the value of said fluid pressure.
 13. The fluid dispensing nozzle means defined in claim 12, wherein said beam comprises spaced beam sections rockably mounted on the body and interconnected by a metal tension strap comprising said tension element.
 14. The fluid dispensing nozzle means defined in claim 12, wherein a heat fusible connection is provided between said beam sections and the tension element to provide said last mentioned release means. 